Regenerator construction of a cold-gas refrigerator



Jan. 1, 1957 J. w. KGHLER ETAL 2,775,875

REGENERATOR CONSTRUCTION OF A COLDGAS REFRIGERATOR Filed Jan. 6, 1955 INVENTORS JACOB WILLEM LAURENS KDHLR mwwbm mwm AGENT Patented Jan. 1, 1957 REGENERATOR CONSTRUCTION OF A COLD-GAS REFRIGERATOR Jacob Willem Laurens Kiihler, Leendert de Lange, and Willem Frederik Schalkwiik, Emmasingel, Eindhoven, Netherlands, assignors to Hartford National haul; and Trust Company, Hartford, Conn., as trustee Application January 6, 1955, Serial No. 480,122

Claims priority, application Netherlands January 19, 1954 3 Claims. (Cl. 62-136) This invention relates to cold-gas refrigerators comprising a space of low temperature and a space of high temperature, which spaces freely communicate with one another by way of a freezer which under normal operating conditions of the refrigerator has a temperature lower than 40 C. and preferably lower than 60 C., a regenerator consisting of wire material, and a cooler. The volume of each space may be varied by means of one or more piston-like bodies. The refrigerator contains a gas which is always in the same state of aggregation and performs a closed thermodynamic cycle.

A cold-gas refrigerator is also known under the name of refrigerator operating on the reversed hot-gas motor principle and it is also known that such machines may be constructed in different ways, for example as a displacer machine or a double-operating machine, as a machine having its cylinder-s at an angle to one another, or as a machine of which the working space is combined with that of a hot-gas piston motor. In such machines it is possible for a considerable temperature diiference to be bridged in one step, that is, by compressing the medium only once for example the machine may have a cooling capacity at -80 C., but also a cooling capacity at 200 C., which temperatures may be reached from room temperature in one step.

It is known that in hot-gas reciprocating machines in general and in cold-gas refrigeartors in particular the regenerator constitutes an important part of the machine. The gas performing a thermodynamic cycle in the machine is cooled once and heated once in the regenerator with each reciprocating movement of the piston-like bodies. The temperature difference bridged by the regenerator may be material, for example 230 C. It is known to provide the regenerator of a cold-gas refrigerator with a filling mass of which the heat-capacity per cm. has a predetermined value which is dependent upon the properties of the engine to thereby ensure a cooling capacity of the machine which is economically justi-fied at the required temperature.

According to the present invention it has been found that in addition to the heat-capacity, the relationship between the length of the regenerator and the hydraulic diameter of the wire material has an important influence upon the cooling capacity and the efiiciency of the refrigerator, since it has been found that it is very desirable that this relationship should be chosen within certain limits. It was found that both the capacity and the chiciency of the refrigerator unduly decreased if the relationship was greater or smaller than the said limits.

According to the invention, the refrigerator is so proportioned that for the length L of the regenenator there applies:

and

L=the length of the regenerator measured in cms. be-

tween the hot and the cold terminal surface.

dn=the hydraulic diameter of the wire material of the regenerator in cms.

. qthe quotient of the absolute temperatures of the cooler and of the freezer.

pmax=the maximum pressure in the cycle in dyne/cm.

n=number of revolutions of the crankshaft of the machine.

=-t-he dynamic viscosity of the gas at the mean temperature of the regenerator in poise.

It will be evident that the said magnitudes are measured under normal operating conditions of the refrigerator. The magnitudes are expressed above in the so-called c. g. s. system, but it is alternatively possible to utilize a difierent system, it being essential only that the magnitudes are expressed in coherent units.

The term hydraulic diameter of the wire material is to be understood in this case to mean the quotient of four times the surface area and the periphery of a section of the wire at right angles to the direction of its length. The term wire is to include also material having a cross-section of which the thickness is smaller than the width, for example a band.

In order that the invention may be readily carried into efiect, it will now be described, by way of example, with reference to one embodiment shown in the accompanying drawing.

The figure shows a coldgas refrigerator which is of the displacer type. A displacer 2 and a piston 3 are adapted to move up and down in a cylinder 1 with a substantially constant phase difference, the displ-acer 3 acting upon the volume of a space 4, the space of low temperature, and both the displacer 2 and the piston 3 acting upon the volume of a space 5, the space of high temperature. Said spaces freely communicate with one another by way of a freezer 6 which under normal operating conditions of the engine has a temperature lower than 40 C., a regenerator 7 and a cooler 8. "Due to the reciprocating movement of the piston-like bodies, substantial expansion occurs in space 4 and substantially compression occurs in space 5.

The displacer 2 is coupled by way of a driving-rod system 9 to a crank of :a crank-shaft 10, while the piston 3 is coupled by way of a driving-rod system 11 to cranks of the same crank-shaft 1d. The refrigerator is driven by an electric motor 12. The regenerator has a height L, indicated by 13.

The above-described machine has a cooler temperature of 300 K. and a freezer temperature of K. The maximum pressure in the cycle is 35.10 dyne/cm. and the number of revolutions per second is 50. The working medium of the machine used in the embodiment shown is hydrogen.

The mean temperature of the regenerator is equal to half the sum of the cooler and the freezer temperature, so in this case From this it follows that P0.23=238, Since ris the temperature of the cooler divided by the temperature of the freezer, there follows for 'r,

is at least andat the most If the hydraulic diameter of the wire material of the regenerator is microns or 2.1O- cm., it follows from the above-m entioned values for that L is at least 1440 2.10- cm.=2.88 cm. and at the most 432O 2.10- =8.64 cm. Preferably L is at least 1770 2.10 =3.54 cm. and at the most If a gas other than hydrogen in the refrigerator would perform a thermodynamic cycle therein, a different value must be filled in for the dynamic viscosity. The values for this viscosity may be found in handbooks.

While we have shown and described the preferred embodiment of our invention, it will be understood that the latter may be embodied otherwise than as herein specifically illustrated or described and that in the illustrated embodiment certain changes in the details of construction and in the arrangement of parts may be made without departing from the underlying idea or principle of the invention within the scope of the appended claims.

What is claimed is:

l. A cold-gasrefrigerator having a gas invariable chemical composition therein comprising a low-temperature space, a high temperature space, a cooler, a regenerator composed of wire material, a freezer having a temperature lower than 40 C, cylinder means, two pistons reciprocating in said cylinder means, said spaces comm-unicating with each other through said cooler, heater and regenerator while said gas performs a closed thermodynamic cycle therein and the volume of said gas being varied in spaces by said reciprocating pistons, the length L of the :regenerator being calculated in accordance with the formula 1 m and L=the length of the regenerator measured in cms. between the hot and cold terminal surface, dn the hydraulic diameter of the wire material of the regenerator in cms., T=the quotient of the absolute temperatures of the cooler and of the freezer, Pmax=th maximum pressure in the cycle in dyne/cnfl, n=number of revolutions of the crankshaft of the machine, and 1 =the dynamic viscosity of the gas at the mean temperature of the regenerator in poise wherein C is equal to at least 3.5.

2. A cold-gas refrigerator as set forth in claim 1 wherein C is at least 3.5 and at the most 10.5.

3. A cold-gas refrigerator having a gas of invariable chemical composition therein comprising a low-temperature space, a high temperature space, a cooler, a regenera-tor composed of wire material, a freezer having a temperature lower than 40 C., cylinder means, at least one piston reciprocating in said cylinder means, said spaces communicating wit-h each other through said cooler, heater and regenerator while said gas performs a closed thermodynamic cycle therein and the volume of said gas being varied in spaces by said reciprocating piston, the length L of the regenerator being calculated in accordance with the formula and L=the length of the regenerator measured in cms. between the hot and cold terminal surface, dn the hydraulic diameter of the wire material of the regenerator in cms, =the quotient of the absolute temperatures of the cooler and of the freezer, pmax hfi maximum pressure in the cycle in dyne/cm. n=number of revolutions of the crankshaft of the machine, and zthe dynamic viscosity of the gas at the mean temperature of the regenerator in poise wherein C is equal to at least 3.5.

References Cited in the file of this patent UNITED STATES PATENTS 1,240,862 Lundgaard Sept. 25, 1917 FOREIGN PATENTS 695,857 Great Britain Aug. 19, 1953 

